Inductance Converter

Inductance is the electrical property of a conductor or coil that causes it to resist changes in current flow by generating a counter-electromotive force (back-EMF). Defined by Faraday's law of electromagnetic induction, inductance links the world of electricity and magnetism: when current through an inductor changes, the associated magnetic flux changes, inducing a voltage that opposes the change. This property underpins the operation of transformers, motors, generators, switching power supplies, RF filters, and countless other electromagnetic devices. This converter supports 22 inductance units spanning all SI prefixes and legacy CGS systems.

The SI unit of inductance is the henry (H), named after American scientist Joseph Henry, who independently discovered electromagnetic induction at roughly the same time as Michael Faraday. One henry is formally defined as the inductance of a circuit in which a change of current at one ampere per second produces an EMF of one volt. Equivalently, 1 H = 1 V·s/A = 1 Wb/A (weber per ampere). The full SI prefix range from exahenry (EH = 10¹⁸ H) to attohenry (aH = 10⁻¹⁸ H) covers all inductance scales from astrophysical plasmas to nanoscale devices.

In practical electronics, the millihenry (mH) and microhenry (µH) are the most commonly encountered units. Power inductors in switch-mode power supplies (SMPS) — used to filter and transform electrical energy in laptops, phone chargers, and electric vehicle powertrains — typically have values between 1 µH and 100 mH. The inductance determines the switching frequency and ripple current of the converter. Higher inductance values give lower ripple current but larger physical size and slower transient response.

At higher frequencies (radio frequency and microwave), the nanohenry (nH) is the working unit. Chip inductors in mobile phone RF front-ends, impedance matching networks, and filter circuits range from 1 nH to a few hundred nH. Printed spiral inductors on PCB substrates typically achieve 5–50 nH. Even a short PCB trace has inductance — approximately 1 nH per millimetre of length — which becomes significant at GHz frequencies and must be accounted for in signal integrity and EMI analysis.

The picohenry (pH) and smaller units describe parasitic inductances in high-speed digital circuits and RF components. The bond wire inside an integrated circuit package contributes 1–5 nH of inductance per millimetre. Via holes in multi-layer PCBs add 0.5–1 nH of inductance per millimetre of board thickness. At 10 GHz, a 1 nH inductance has an impedance of 62.8 Ω — significant enough to cause signal reflections, power delivery noise, and EMI radiation. Understanding and minimising parasitic inductance is a core skill in high-speed PCB design.

At the large end, inductances of henrys appear in power system inductors, audio crossover chokes, and superconducting magnetic energy storage (SMES) systems. MRI superconducting magnets have inductances of several henrys, storing enormous magnetic energy (E = ½LI²) in their persistent current loops — a 10 H magnet carrying 100 A stores 50,000 joules. Power system synchronous generators have subtransient inductances (used in fault current calculations) typically between 0.1 H and 1 H per phase.

The abhenry (CGS-EMU, = 10⁻⁹ H = 1 nH) and stathenry (CGS-ESU, ≈ 8.9876 × 10¹¹ H ≈ 899 GH) are the legacy CGS inductance units. The abhenry is notably practical — it equals one nanohenry, the unit routinely encountered in RF work. The stathenry's enormous magnitude (nearly one terahenry) reflects the fundamental incompatibility of CGS-ESU units with practical electromagnetic measurements. The weber per ampere (Wb/A) is algebraically identical to the henry and appears in transformer and motor design literature.

This converter provides instant conversion between all 22 inductance units: henry [H], exahenry [EH], petahenry [PH], terahenry [TH], gigahenry [GH], megahenry [MH], kilohenry [kH], hectohenry [hH], dekahenry [daH], decihenry [dH], centihenry [cH], millihenry [mH], microhenry [µH], nanohenry [nH], picohenry [pH], femtohenry [fH], attohenry [aH], weber/ampere [Wb/A], abhenry [abH], EMU of inductance, stathenry [stH], and ESU of inductance. Enter your value, select units, and get the result instantly.